@DragonLady, welcome to the board.
- You might benefit from reviewing Unable to integrate G’MIC into GIMP, It is Gimp 2.x -centric, but covers some of the basic troubleshooting steps.
- GIMP and G’MIC need to agree on plugin location. Start your 3.0.2-1 Gimp, and load an image. Is GMIC-Qt listed in the Gimp Filters menu listing?
- If not, check where Gimp looks for plug-ins. Open Edit ⇒ Preferences; the Preferences dialog box has a left hand preference item tree.
- Scroll down to the “Folders” item, and, if that item is preceded by a “+” sign, click on that sign so that it changes to a “–” and provides an additional list of folders. Locate the Plug-ins choice and click on it
- The Preference dialog box should change and look (something) like this.
Your entries will be quite different. - These are the paths to the folders in which Gimp checks for plug-ins, the latest
gimp_gmic_qt.exebinary executable should be in one of these folders. - Normally the G’MIC Windows installer finds the correct plug-in folder, but if you have recently upgraded from 2.10 using a Windows uninstall/Windows installer cycle, some mismatch is possible; Windows uninstall preserves folders that users may have changed and in some circumstances this may cause
gimp_gmic_qtbinary executable to go into a folder that Gimp 3.0.2 has not been set up to use.
You may also follow the ‘nuclear’ option that @alain took - do a deep uninstall of both GIMP and G’MIC. By ‘deep uninstall’ I mean running the Windows uninstaller on both GIMP and G’MIC and manually removing folders and files that the uninstallers preserve.
Hope this helps.